1. Field of the Invention
This invention relates generally to methods of making coated articles, such as but not limited to tabletops, shower doors, partitions, and vehicle transparencies, and to the articles made thereby.
2. Technical Considerations
In today's automotive market, a heavy emphasis is placed on automotive styling. The way a vehicle looks can be as important to vehicle sales as the vehicle's mechanical reliability or safety rating. Therefore, automotive manufacturers have gone to great lengths to enhance vehicle styling. These styling enhancements include providing more color selections to the consumer and also providing colors having metallic flakes to provide the vehicle with a “polychromatic effect”.
While these styling enhancements have been generally well received by consumers, a problem to date is that even with the new vehicle paint finishes, the automotive transparencies (such as but not limited to windshields, side lights, back lights, moon roofs, and sunroofs) continue to be generally gray or neutral colored. While providing solar control properties, these conventional transparencies provide little enhancement to the vehicle styling.
In nonautomotive fields, it has been known to provide coated articles in which a color is generated by the interference effect between a substrate and a coating. As will be appreciated by one skilled in the art, the term “interference effect” refers to the variation of electromagnetic wave amplitude with distance or time, caused by the superposition of waves of electromagnetic radiation (for example, visible light). These waves can be the result of reflection or transmission at the interfaces of one or more layers in an optical thin film coating. For example, U.S. Pat. No. 6,164,777 discloses a plastic contact lens having an interference coating made of alternating materials of different refractive indices. U.S. Pat. No. 5,923,471 discloses a “hot mirror” for a heat lamp having alternating layers of zirconia and silica. U.S. Publication No. US 2003/0031842 A1 discloses an article with a patterned appearance provided by a visually observable contrast between one or more generally transparent thin film coatings. Other examples of interference coatings and coated articles are disclosed in U.S. Pat. Nos. 5,619,059; 4,902,581; and 5,112,693; and Swiss Patent No. 339575.
While these disclosed coatings are suitable for their intended purpose, numerous other considerations must be addressed in trying to incorporate an interference coating into an automotive transparency. For example, in the United States, government regulations require that all windshields must have a luminous (visible) light transmittance (Lta) of at least 70%. In Europe, the required minimum Lta is 75%. The presence of an interference coating could adversely impact upon the light transmittance of the transparency.
It would be advantageous to provide a method of making an automotive transparency that is aesthetically pleasing and could be used to enhance the styling of a vehicle. It would also be advantageous to provide an automotive transparency that provides the opportunity to color coordinate or match the color of the transparency with the paint color of the vehicle. It would further be advantageous if such a transparency also met the mandated government requirements for automotive transparencies.